1. Field of the Invention
The present invention relates to a sheet supplying device for use in a copier, a printer and the like.
2. Description of the Related Art
An apparatus supplied with a sheet material, for example, a copier which is supplied with copying sheets, such as paper, is provided with a sheet supplying device. The sheet supplying device is provided with a plurality of sheet supplying cassettes with each cassette corresponding to a plurality of sizes of the sheet. A lateral transport for transporting a sheet in the direction of its width is more preferable in view of the transport speed than a longitudinal transport for transporting a sheet in its longitudinal direction. There exists a copier which enables the lateral transport of even large-sized sheets such as B4- and A3-sized sheets.
On the contrary, in order to transport such a large-sized sheet in the lateral direction, it is required that the photoconductive drum, the transport roller, the transport path, etc. in the copier are also large, resulting in the increase of size and cost of the copier. Therefore, a method is preferably used for transporting a large-sized sheet, such as B4-, A3-sized sheets, in the longitudinal direction, while transporting a small-sized sheets, such as sheets of not larger than A4-size, in the lateral direction.
However, in the case, for example, where the copier has a variable magnification function for reducing or enlarging an image, the copier needs B5R- and A4R-sheet cassettes for a longitudinal transport in a reduction copying operation, and further needs B5 and A4-sheet cassettes for a lateral transport in a normal copying operation in consideration of the transport speed. If such various types of cassettes are used in the copier, it is required that the sheet supplying device shall be large to accommodate all of those cassettes, or that one of those cassettes shall be selected and exchanged at the sheet supplying device according to the purpose of each copying operation. As a result, this makes the copier large and thus increases the cost, or complicates the copying operation and thus increases the operation time.
Thus, in order to solve the above problem, a conventional sheet supplying device has been proposed, wherein a common cassette is used for supplying a same sized sheet in two different transport orientations, for example, a common cassette for B5 and B5R and a common cassette for A4 and A4R are used, and the switching between the lateral transport and the longitudinal transport is done by turning the cassette, as disclosed in the Japanese Patent Application Laying Open (KOKAI) No. 56-59245, No. 59-123859, etc.
However, in the above conventional supplying device, the following problem arises: that is, since in a conventional copier, the maximum size of a sheet capable of being supplied is limited by mechanical conditions, such as the length of a photoconductive drum in the copier's main body, the length of a developing magnet roller, the width of the sheet transport path and so on, the sheet sometimes cannot be fed to the main body of the copier, depending upon the size of the sheet, for example, when the transport orientation of the sheet is changed from the orientation for longitudinal transport to the orientation for lateral transport by turning a turning cassette in the above conventional apparatus. In this case, the turning of the turning cassette results in a useless motion with wasting time and energy, and maybe causing a mechanical trouble. Therefore, it has been desired to develop a device to alleviate the above disadvantage.